Some communication protocols utilize multiple transmission modes. Often, these modes are developed to allow increased bandwidth or signal to noise ratios. These protocol enhancements occur in the physical layer of the network, which is often referred to as the PHY.
For example, Ethernet has evolved from 10 Mbps to 1 Gps. Other protocols, such as USB and others, have also experienced an evolution in bandwidth. Often, a negotiation is conducted between two nodes to determine which of the plurality of transmission modes should be used. For example, each node may default to a PHY mode which all nodes must accommodate. Messages may then be sent between two nodes using this default PHY mode to determine whether a different PHY mode can be employed.
This trend also exists within wireless protocols. For example, Bluetooth has recently introduced higher bandwidth versions, such as Bluetooth 2.0, Bluetooth 3.0 and BLE (Bluetooth Low Energy). As suggested above, a negotiation is conducted between Bluetooth devices to determine the PHY mode that will be used for transmission between the two devices. For example, Bluetooth defines a sequence of packet data units (PDUs) that are exchanged between a master and slave to determine the optimal PHY protocol to use. For example, the master will send the slave a PHY request PDU. That PHY request PDU contains the preferred PHY mode that the master wishes to use for transmission and receipt. In response, the slave transmits a PHY response PDU. That response contains the preferred PHY mode that the slave wishes to use for transmission and receipt. The master then determines the optimal PHY modes to use for transmission in each direction based on the contents of the two PDUs. That determination is transmitted to the slave using a PHY update PDU. From this point forward, communications between the master and slave take place using these negotiated PHY mode settings.
This negotiation is inefficient as it requires several PDUs to be transmitted between the master and slave before a PHY mode switch can be initiated.
It would be beneficial if there were a system where the PHY mode could be automatically detected and the receiver could automatically switch to that detected PHY mode. Such a system would eliminate the need for inefficient and time consuming negotiations between devices.